Fix script broken

Traceback:

```
Start
Traceback (most recent call last):
File "fixfonts.py", line 264, in
main()
File "fixfonts.py", line 250, in main
ttfs_gf = download_gf_family(font.familyName)
File "/Users/dcrossland/src/github.com/googlefonts/gf-glyphs-scripts/Google Fonts/utils.py", line 66, in download_gf_family
return fonts_from_zip(family_zip)
File "/Users/dcrossland/src/github.com/googlefonts/gf-glyphs-scripts/Google Fonts/utils.py", line 58, in fonts_from_zip
ttfs.append(TTFont(zipfile.open(file_name)))
File "/Library/Python/2.7/site-packages/fonttools-3.25.0-py2.7.egg/fontTools/ttLib/ttFont.py", line 126, in __init__
file.seek(0)
io.UnsupportedOperation: seek
End
```

Start at Google Fonts/utils.py line 58, called by download_gf_family on line 66 and fixfonts.py main on line 250. Reproduce the failure with fixfonts.py and inspect the fontTools TTFont input shown in the traceback. Done means the script proceeds past font loading without the reported io.UnsupportedOperation error.

Written by the indexing model from the issue text.